From DOS to Linux HOWTO
By Guido Gonzato
v1.0, 11 December 1996
This HOWTO is dedicated to all the (soon to be former?) DOS users who
have just taken the plunge and decided to switch to Linux, the free
Unix clone for 386+ computers. Given the similarities between DOS and
Unix, the purpose of this document is to help the reader translate his
or her knowledge of DOS into the Linux environment, so as to be pro­
ductive asap.
1. Introduction
1.1. Is Linux Right for You?
You want to switch from DOS to Linux? Good idea, but beware: it might
not be useful for you. IMHO, there is no such thing as ``the best
computer'' or ``the best operating system'': it depends on what one
has to do. That's why I don't believe that Linux is the best solution
for everyone, even if it is technically superior to many commercial
oses. You're going to benefit immensely from Linux if what you need is
sw for programming, the Internet, TeX... technical sw in general, but
if you mostly need commercial sw, or if you don't feel like learning
and typing commands, look elsewhere.
Linux is not (for now) as easy to use and configure as Windows or the
Mac, so be prepared to hack quite a bit. In spite of these warnings,
let me tell you that I'm 100% confident that if you belong to the
right user type you'll find in Linux your computer Nirvana. It's up to
you. And remember that Linux + DOS/Windows can coexist on the same
machine, anyway.
Prerequisites for this howto: I'll assume that
· you know the basic DOS commands and concepts;
· Linux, possibly with X Window System, is properly installed on your
PC;
· your shell---the equivalent of COMMAND.COM---is bash;
· you understand that this guide is only an incomplete primer. For
more information, please refer to Matt Welsh's ``Linux Installation
and Getting Started'' and/or Larry Greenfield's ``Linux User
Guide'' (sunsite.unc.edu:/pub/Linux/docs/LDP).
This howto replaces the old ``From DOS to Linux - Quick!'' mini-howto.
1.2. It Is. Tell Me More
You installed Linux and the programs you needed on the PC. You gave
yourself an account (if not, type adduser now!) and Linux is running.
You've just entered your name and password, and now you are looking at
the screen thinking: ``Well, now what?''
Now, don't despair. You're almost ready to do the same things you used
to do with DOS, and many more. If you were running DOS instead of
Linux, you would be doing some of the following tasks:
· running programs and creating, copying, viewing, deleting,
printing, renaming files;
· CD'ing, MD'ing, RD'ing, and DIR'ring your directories;
· formatting floppies and copying files from/to them;
· mending your AUTOEXEC.BAT and CONFIG.SYS;
· writing your own .BAT files and/or QBasic programs;
· the remaining 1%.
You'll be glad to know that these tasks can be accomplished under
Linux in a fashion similar to DOS. Under DOS, the average user uses
very few of the 100+ commands available: the same, up to a point,
holds for Linux.
A few things to point out before going on:
· first, how to get out. To quit Linux: if you see a textmode screen,
press CTRL-ALT-DEL, wait for the system to fix its innards and tell
you everything is OK, then switch off the PC. If you are working
under X Window System, press CTRL-ALT-BACKSPACE first, then CTRL-
ALT-DEL. Never switch off or reset the PC directly: it may damage
the filesystem;
· unlike DOS, Linux has built-in security mechanisms, due to its
multiuser nature. Files and directories have permissions associated
to them, and therefore some cannot be accessed by the normal user;
(see Section ``Permissions''). only the user whose login name is
``root'' has the power. (This guy's the system administrator. If
you work on your own PC, you'll be root as well.) DOS, on the
contrary, will let you wipe out the entire contents of your hard
disk;
· you are strongly encouraged to experiment, play, try by yourself:
it surely won't hurt. You can get some help typing at the prompt ($
is the standard prompt, # is the prompt for root):
$ help
(this gives help about bash), or get info about a command typing
$ man command
which, if you have installed the man pages, will invoke the manual
(``man'') page associated to command. You may also try:
$ apropos command
$ whatis command
and press 'q' to exit;
· most of the power and flexibility of Unix comes from the simple
concepts of redirection and piping, more powerful than under DOS.
Simple commands can be strung together to accomplish complex tasks.
Do use these features!
· conventions: means something that must be specified, while
[...] something optional. Example:
$ tar -tf [> redir_file]
file.tar must be indicated, but redirection to redir_file is optional.
· from now on ``RMP'' means ``please read the man pages for further
information''.
1.3. For the Impatient
Want to strike out? Have a look at this:
DOS Linux Notes
------------------------------------------------------------------------------
BACKUP tar -Mcvf device dir/ completely different
CD dirname\ cd dirname/ almost the same syntax
COPY file1 file2 cp file1 file2 ditto
DEL file rm file beware - no undelete
DELTREE dirname rm -R dirname/ ditto
DIR ls not exactly the same syntax
EDIT file vi file I think you won't like it
emacs file this is better
jstar file feels like dos' edit
FORMAT fdformat,
mount, umount quite different syntax
HELP command man command same philosophy
MD dirname mkdir dirname/ almost the same syntax
MOVE file1 file2 mv file1 file2 ditto
NUL /dev/null ditto
PRINT file lpr file ditto
PRN /dev/lp0,
/dev/lp1 ditto
RD dirname rmdir dirname/ almost the same syntax
REN file1 file2 mv file1 file2 not for multiple files
RESTORE tar -Mxpvf device different syntax
TYPE file less file much better
WIN startx poles apart!
If you need more than a table of commands, please refer to the
following sections.
2. Files and Programs
2.1. Files: Preliminary Notions
Linux has a file system---meaning by that ``the structure of
directories and files therein''---very similar to that of DOS. Files
have filenames that obey special rules, are stored in directories,
some are executable, and among these most have command switches.
Moreover, you can use wildcard characters, redirection, and piping.
There are only a few minor differences:
· under DOS, file names are in the so-called 8.3 form; e.g.
NOTENOUG.TXT. Under Linux we can do better. If you installed Linux
using a filesystem like ext2 or umsdos, you can use longer
filenames (up to 255 characters), and with more than one dot in
them: for example, This_is.a.VERY_long.filename. Please note that I
used both upper and lower case characters: in fact...
· upper and lower case characters in file names or commands are
different. Therefore, FILENAME.tar.gz and filename.tar.gz are two
different files. ls is a command, LS is a mistake;
· there are no compulsory exensions like .COM and .EXE for programs,
or .BAT for batch files. Executable files are marked by an asterisk
For example:
$ ls -F
letter_to_Joe cindy.jpg cjpg* I_am_a_dir/ my_1st_script* old~
The files cjpg* and my_1st_script* are executable---``programs''.
Under DOS, backup files end in .BAK, while under Linux they end with a
tilde '~'. Further, a file whose name starts with a dot is considered
as hidden. Example: the file .I.am.a.hidden.file won't show up after
the ls command;
· DOS program switches are obtained with /switch, Linux switches with
-switch or --switch. Example: dir /s becomes ls -R. Note that many
DOS programs, like PKZIP or ARJ, use Unix-style switches.
You can now jump to Section ``Translating Commands from DOS to
Linux'', but if I were you I'd read on.
2.2. Symbolic Links
Unix has a type of file that doesn't exist under DOS: the symbolic
link. This can be thought of as a pointer to a file or to a directory,
and can be used instead of the file or directory it points to; it's
similar to Win 95 shortcuts. Examples of symbolic links are /usr/X11,
which points to /usr/X11R6; /dev/modem, which points to either
/dev/cua0 or /dev/cua1.
To make a symbolic link:
$ ln -s
Example:
$ ln -s /usr/doc/g77/DOC g77manual.txt
Now you can refer to g77manual.txt instead of /usr/doc/g77/DOC.
2.3. Permissions and Ownership
DOS files and directories have the following attributes: A (archive),
H (hidden), R (read-only), and S (system). Only H and R make sense
under Linux: hidden files start with a dot, and for the R attribute,
read on.
Under Unix a file has ``permissions'' and an owner, who belongs to a
``group''. Look at this example:
$ ls -l /bin/ls
-rwxr-xr-x 1 root bin 27281 Aug 15 1995 /bin/ls*
The first field contains the permissions of the file /bin/ls, which
belongs to root, group bin. Leaving the remaining information aside
(Matt's book is there for that purpose), remember that -rwxr-xr-x
means (from left to right):
- is the file type (- = ordinary file, d = directory, l = link, etc);
rwx are the permissions for the file owner (read, write, execute); r-x
are the permissions for the group of the file owner (read, execute);
(I won't cover the concept of group, you can survive without it as
long as you're a beginner ;-) r-x are the permissions for all other
users (read, execute).
This is why you can't delete the file /bin/ls unless you are root: you
don't have the write permission to do so. To change a file's
permissions, the command is:
$ chmod
where who is u (user, that is owner), g (group), o (other), X is
either + or -, perm is r (read), w (write), or x (execute). Examples:
$ chmod u+x file
this sets the execute permission for the file owner. Shortcut: chmod
+x file.
$ chmod go-wx file
this removes write and execute permission for everyone but the owner.
$ chmod ugo+rwx file
this gives everyone read, write, and execute permission.
# chmod +s file
this makes a so-called ``setuid'' or ``suid'' file---a file that
everyone can execute with root privileges.
A shorter way to refer to permissions is with numbers: rwxr-xr-x can
be expressed as 755 (every letter corresponds to a bit: --- is 0, --x
is 1, -w- is 2, -wx is 3...). It looks difficult, but with a bit of
practice you'll understand the concept.
root, being the so-called superuser, can change everyone's file
permissions. There's more to it---RMP.
2.4. Translating Commands from DOS to Linux
On the left, the DOS commands; on the right, their Linux counterpart.
COPY: cp
DEL: rm
MOVE: mv
REN: mv
TYPE: more, less, cat
Redirection and plumbing operators: < > >> |
Wildcards: * ?
nul: /dev/null
prn, lpt1: /dev/lp0 or /dev/lp1; lpr
- EXAMPLES -
DOS Linux
---------------------------------------------------------------------
C:\GUIDO>copy joe.txt joe.doc $ cp joe.txt joe.doc
C:\GUIDO>copy *.* total $ cat * > total
C:\GUIDO>copy fractals.doc prn $ lpr fractals.doc
C:\GUIDO>del temp $ rm temp
C:\GUIDO>del *.bak $ rm *~
C:\GUIDO>move paper.txt tmp\ $ mv paper.txt tmp/
C:\GUIDO>ren paper.txt paper.asc $ mv paper.txt paper.asc
C:\GUIDO>print letter.txt $ lpr letter.txt
C:\GUIDO>type letter.txt $ more letter.txt
C:\GUIDO>type letter.txt $ less letter.txt
C:\GUIDO>type letter.txt > nul $ cat letter.txt > /dev/null
n/a $ more *.txt *.asc
n/a $ cat section*.txt | less
Notes:
· * is smarter under Linux: * matches all files except the hidden
ones; .* matches all hidden files; *.* matches only those that have
a '.' in the middle, followed by other characters; p*r matches
both `peter' and `piper'; *c* matches both `picked' and `peck';
· when using more, press SPACE to read through the file, `q' or CTRL-
C to exit. less is more inuitive and lets you use the arrow keys;
· there is no UNDELETE, so think twice before deleting anything;
· in addition to DOS's < > >>, Linux has 2> to redirect error
messages (stderr); moreover, 2>&1 redirects stderr to stdout, while
1>&2 redirects stdout to stderr;
· Linux has another wildcard: the []. Use: [abc]* matches files
starting with a, b, c; *[I-N,1,2,3] matches files ending with I, J,
K, L, M, N, 1, 2, 3;
· there is no DOS-like RENAME; that is, mv *.xxx *.yyy won't work;
· use cp -i and mv -i to be warned when a file is going to be
overwritten.
2.5. Running Programs: Multitasking and Sessions
To run a program, type its name as you would do under DOS. If the
directory (Section ``Directories'') where the program is stored is
included in the PATH (Section ``System Initialization''), the program
will start. Exception: unlike DOS, under Linux a program located in
the current directory won't run unless the directory is included in
the PATH. Escamotage: being prog your program, type ./prog.
This is what the typical command line looks like:
$ command -s1 -s2 ... -sn par1 par2 ... parn < input > output
where -s1, ..., -sn are the program switches, par1, ..., parn are the
program parameters. You can issue several commands on the command
line:
$ command1 ; command2 ; ... ; commandn
That's all about running programs, but it's easy to go a step beyond.
One of the main reasons for using Linux is that it is a multitasking
os---it can run several programs (from now on, processes) at the same
time. You can launch processes in background and continue working
straight away. Moreover, Linux lets you have several sessions: it's
like having many computers to work on at once!
· To switch to session 1..6:
$ ALT-F1 ... ALT-F6
· To start a new session without leaving the current one:
$ su -
Example:
$ su - root
This is useful, for one, when you need to mount a disk (Section
``Floppies''): normally, only root can do that.
· To end a session:
$ exit
If there are stopped jobs (see later), you'll be warned.
· To launch a process in foreground:
$ progname [-switches] [parameters] [< input] [> output]
· To launch a process in background, add an ampersand '&' at the end
of the command line:
$ progname [-switches] [parameters] [< input] [> output] &
[1] 123
the shell identifies the process with a job number (e.g. [1]; see
below), and with a PID (123 in our example).
· To see how many processes there are:
$ ps -a
This will output a list of currently running processes.
· To kill a process:
$ kill
You may need to kill a process when you don't know how to quit it the
right way... ;-). Sometimes, a process will only be killed by either
of the following:
$ kill -15
$ kill -9
In addition to this, the shell allows you to stop or temporarily sus­
pend a process, send a process to background, and bring a process from
background to foreground. In this context, processes are called
``jobs''.
· To see how many jobs there are:
$ jobs
here jobs are identified by their job number, not by their PID.
· To stop a process running in foreground (it won't always work):
$ CTRL-C
· To suspend a process running in foreground (ditto):
$ CTRL-Z
· To send a suspended process into background (it becomes a job):
$ bg
· To bring a job to foreground:
$ fg
· To kill a job:
$ kill
where may be 1, 2, 3, ... Using these commands you can format a
disk, zip a bunch of files, compile a program, and unzip an archive
all at the same time, and still have the prompt at your disposal. Try
this with DOS! And try with Windows, just to see the difference in
performance.
2.6. Running Programs on Remote Computers
To run a program on a remote machine whose IP address is
remote.bigone.edu, you do:
$ telnet remote.bigone.edu
After logging in, start your favourite program. Needless to say, you
must have an account on the remote machine.
If you have X11, you can even run an X application on a remote
computer, displaying it on your X screen. Let remote.bigone.edu be the
remote X computer and local.linux.box be your Linux machine. To run
from local.linux.box an X program that resides on remote.bigone.edu,
do the following:
· fire up X11, start an xterm or equivalent terminal emulator, then
type:
$ xhost +remote.bigone.edu
$ telnet remote.bigone.edu
· after logging in, type:
remote:$ DISPLAY=local.linux.box:0.0
remote:$ progname &
(instead of DISPLAY..., you may have to write setenv DISPLAY
local.linux.box:0.0. It depends on the remote shell.)
Et voila! Now progname will start on remote.bigone.edu and will be
displayed on your machine. Don't try this over a ppp line, though.
3. Using Directories
3.1. Directories: Preliminary Notions
We have seen the differences between files under DOS and Linux. As for
directories, under DOS the root directory is under Linux / is.
Similarly, nested directories are separated by under DOS, by / under
Linux. Example of file paths:
DOS: C:\PAPERS\GEOLOGY\MID_EOC.TEX
Linux: /home/guido/papers/geology/mid_eocene.tex
As usual, .. is the parent directory, . is the current directory.
Remember that the system won't let you cd, rd, or md everywhere you
want. Each user starts from his or her own directory called dir is
/home/guido.
3.2. Directories Permissions
Directories, too, have permissions. What we have seen in Section
``Permissions'' holds for directories as well (user, group, and
other). For a directory, rx means you can cd to that directory, and w
means that you can delete a file in the directory (according to the
file's permissions, of course), or the directory itself.
For example, to prevent other users from snooping in /home/guido/text:
$ chmod o-rwx /home/guido/text
3.3. Translating Commands from DOS to Linux
DIR: ls, find, du
CD: cd, pwd
MD: mkdir
RD: rmdir
DELTREE: rm -R
MOVE: mv
- EXAMPLES -
DOS Linux
---------------------------------------------------------------------
C:\GUIDO>dir $ ls
C:\GUIDO>dir file.txt $ ls file.txt
C:\GUIDO>dir *.h *.c $ ls *.h *.c
C:\GUIDO>dir/p $ ls | more
C:\GUIDO>dir/a $ ls -l
C:\GUIDO>dir *.tmp /s $ find / -name "*.tmp"
C:\GUIDO>cd $ pwd
n/a - see note $ cd
ditto $ cd ~
ditto $ cd ~/temp
C:\GUIDO>cd \other $ cd /other
C:\GUIDO>cd ..\temp\trash $ cd ../temp/trash
C:\GUIDO>md newprogs $ mkdir newprogs
C:\GUIDO>move prog .. $ mv prog ..
C:\GUIDO>md \progs\turbo $ mkdir /progs/turbo
C:\GUIDO>deltree temp\trash $ rm -R temp/trash
C:\GUIDO>rd newprogs $ rmdir newprogs
C:\GUIDO>rd \progs\turbo $ rmdir /progs/turbo
Notes:
1. when using rmdir, the directory to remove must be empty. To delete
a directory and all of its contents, use rm -R (at your own risk).
2. the character '~' is a shortcut for the name of your home
directory. The commands cd or cd ~ will take you to your home
directory from wherever you are; the command cd ~/tmp will take you
to /home/your_home/tmp.
3. cd - ``undoes'' the last cd.
4. Floppies, Hard Disks, and the Like
4.1. Managing Devices
You have never thought about it, but the DOS command FORMAT A: does a
lot more work than it seems. In fact, when you issue the command
FORMAT it will: 1) physically format the disk; 2) create the A:
directory (= create a filesystem); 3) make the disk available to the
user (= mount the disk).
These three steps are addressed separately under Linux. You can use
floppies in MS-DOS format, though other formats are available and are
better---the MS-DOS format won't let you use long filenames. Here is
how to prepare a disk (you'll need to start a session as root):
· To format a standard 1.44 meg floppy disk (A:):
# fdformat /dev/fd0H1440
· To create a filesystem:
# mkfs -t ext2 -c /dev/fd0H1440
or
# mformat a:
to create an MS-DOS filesystem. Before using the disk, you must mount
it.
· To mount the disk:
# mount -t ext2 /dev/fd0 /mnt
or
# mount -t msdos /dev/fd0 /mnt
Now you can address the files in the floppy. When you've finished,
before extracting the disk you must unmount it.
· To unmount the disk:
# umount /mnt
Now you can extract the disk. Obviously, you have to fdformat and mkfs
only unformatted disks, not previously used ones. If you want to use
drive B:, refer to fd1H1440 and fd1 instead of fd0H1440 and fd0 in the
examples above.
All you used to do with A: or B: is now done using /mnt instead.
Examples:
DOS Linux
---------------------------------------------------------------------
C:\GUIDO>dir a: $ ls /mnt
C:\GUIDO>copy a:*.* $ cp /mnt/* /docs/temp
C:\GUIDO>copy *.zip a: $ cp *.zip /mnt/zip
C:\GUIDO>a: $ cd /mnt
A:>_ /mnt/$ _
Needless to say, what holds for floppies also holds for other devices;
for instance, you may want to mount another hard disk or a CD-ROM
drive. Here's how to mount the CD-ROM:
# mount -t iso9660 /dev/cdrom /mnt
This was the ``official'' way to mount your disks, but there's a trick
in store. Since it's a bit of a nuisance having to be root to mount a
floppy or a CD-ROM, every user can be allowed to mount them this way:
· as root, create the directories /mnt/a, /mnt/a:, and /mnt/cdrom
· add in /etc/fstab the following lines:
/dev/cdrom /mnt/cdrom iso9660 ro,user,noauto 0 0
/dev/fd0 /mnt/a: msdos user,noauto 0 0
/dev/fd0 /mnt/a ext2 user,noauto 0 0
Now, to mount a DOS floppy, an ext2 floppy, and a CD-ROM:
$ mount /mnt/a:
$ mount /mnt/a
$ mount /mnt/cdrom
/mnt/a, /mnt/a:, and /mnt/cdrom can now be accessed by every user.
I've found that to write on /mnt/a without being root, right after
preparing the floppy it's necessary to do:
# mount /mnt/a
# chmod 777 /mnt/a
# umount /mnt/a
Remember that allowing anyone to mount disks this way is a gaping
security hole, if you care.
4.2. Backing Up
Now that you know how to handle floppies etc., a couple of lines to
see how to do your backup. There are several packages to help you, but
the very least you can do for a multi-volume backup is (as root):
# tar -M -cvf /dev/fd0H1440 /dir_to_backup
Make sure to have a formatted floppy in the drive, and several ready.
To restore your stuff, insert the first floppy in the drive and do:
# tar -M -xpvf /dev/fd0H1440
5. Tayloring the System
5.1. System Initialization Files
Two important files under DOS are AUTOEXEC.BAT and CONFIG.SYS, which
are used at boot time to initialise the system, set some environment
variables like PATH and FILES, and possibly launch a program or batch
file. Under Linux there are several initialisation files, some of
which you had better not tamper with until you know exactly what you
are doing. I'll tell you what the most important are, anyway:
FILES NOTES
/etc/inittab don't touch for now!
/etc/rc.d/* ditto
If all you need is setting the PATH and other environment variables,
or you want to change the login messages or automatically launch a
program after the login, have a look at the following files:
FILES NOTES
/etc/issue sets pre-login message
/etc/motd sets post-login message
/etc/profile sets PATH and other variables, etc.
/etc/bashrc sets aliases and functions, etc. (see below)
/home/your_home/.bashrc sets your aliases + functions
/home/your_home/.bash_profile sets environment + starts your progs
/home/your_home/.profile ditto
If the latter file exists (note that it is a hidden file), it will be
read after the login and the commands in it will be executed.
Example---look at this .profile:
______________________________________________________________________
# I am a comment
echo Environment:
printenv | less # equivalent of command SET under DOS
alias d='ls -l' # easy to understand what an alias is
alias up='cd ..'
echo "I remind you that the path is "$PATH
echo "Today is `date`" # use the output of command 'date'
echo "Have a good day, "$LOGNAME
# The following is a "shell function"
ctgz() # List the contents of a .tar.gz archive.
{
for file in $*
do
gzip -dc ${file} | tar tf -
done
}
# end of .profile
______________________________________________________________________
PATH and LOGNAME, you guessed right, are environment variables. There
are many others to play with; for instance, RMP for apps like less.
5.2. Program Initialization Files
Under Linux, virtually everything can be tailored to your needs. Most
programs have one or more initialization files you can fiddle with,
often as a .prognamerc in your home dir. The first ones you'll want to
modify are:
/usr/lib/X11/fvwm/system.fvwmrc
programs.
For all of these and the others you'll come across sooner or later,
RMP.
6. A Bit of Programming
6.1. Shell Scripts: .BAT Files on Steroids
If you used .BAT files to create shortcuts of long command lines (I
did a lot), this goal can be attained by inserting appropriate alias
lines (see example above) in profile or .profile. But if your .BATs
were more complicated, then you'll love the scripting language made
available by the shell: it's as powerful as QBasic, if not more. It
has variables, structures like while, for, case, if... then... else,
and lots of other features: it can be a good alternative to a ``real''
programming language.
To write a script---the equivalent of a .BAT file under DOS---all you
have to do is write a standard ASCII file containing the instructions,
save it, then make it executable with the command chgmod +x
. To execute it, type its name.
A word of warning. The system editor is called vi, and in my
experience most new users find it very difficult to use. I'm not going
to explain how to use it, because I don't like it and don't use it, so
there. See Matt Welsh's ``Linux installation...'', pag. 109. (You had
better get hold of another editor like joe or emacs for X.) Suffice it
here to say that:
· to insert some text, type 'i' then your text;
· to quit vi whithout saving, type then :q!
· to save and quit, type then :wq
Writing scripts under bash is such a vast subject it would require a
book by itself, and I will not delve into the topic any further. I'll
just give you an example of shell script, from which you can extract
some basic rules:
______________________________________________________________________
#!/bin/sh
# sample.sh
# I am a comment
# don't change the first line, it must be there
echo "This system is: `uname -a`" # use the output of the command
echo "My name is $0" # built-in variables
echo "You gave me the following $# parameters: "$*
echo "First parameter is: "$1
echo -n "What's your name? " ; read your_name
echo look the difference: "hi $your_name" # quoting with "
echo look the difference: 'hi $your_name' # quoting with '
DIRS=0 ; FILES=0
for file in `ls .` ; do
if [ -d ${file} ] ; then # if file is a directory
DIRS=`expr $DIRS + 1` # DIRS = DIRS + 1
elif [ -f ${file} ] ; then
FILES=`expr $FILES + 1`
fi
case ${file} in
*.gif|*jpg) echo "${file}: graphic file" ;;
*.txt|*.tex) echo "${file}: text file" ;;
*.c|*.f|*.for) echo "${file}: source file" ;;
*) echo "${file}: generic file" ;;
esac
done
echo "there are ${DIRS} directories and ${FILES} files"
ls | grep "ZxY--!!!WKW"
if [ $? != 0 ] ; then # exit code of last command
echo "ZxY--!!!WKW not found"
fi
echo "enough... type 'man bash' if you want more info."
______________________________________________________________________
6.2. C for Yourself
Under Unix, the system language is C, love it or hate it. Scores of
other languages (FORTRAN, Pascal, Lisp, Basic, Perl, awk...) are also
available.
Taken for granted that you know C, here are a couple of guidelines for
those of you who have been spoilt by Turbo C++ or one of its DOS
brothers. Linux's C compiler is called gcc and lacks all the bells and
whistles that usually accompany its DOS counterparts: no IDE, on-line
help, integrated debugger, etc. It's just a rough command-line
compiler, very powerful and efficient. To compile your standard
hello.c you'll do:
$ gcc hello.c
which will create an executable file called a.out. To give the
executable a different name, do
$ gcc -o hola hello.c
To link a library against a program, add the switch -l. For
example, to link the math library:
$ gcc -o mathprog mathprog.c -lm
(The -l switch forces gcc to link the library
/usr/lib/lib.a; so -lm links /usr/lib/libm.a).
So far, so good. But when your prog is made of several source files,
you'll need to use the utility make. Let's suppose you have written an
expression parser: its source file is called parser.c and #includes
two header files, parser.h and xy.h. Then you want to use the routines
in parser.c in a program, say, calc.c, which in turn #includes
parser.h. What a mess! What do you have to do to compile calc.c?
You'll have to write a so-called makefile, which teaches the compiler
the dependencies between sources and objects files. In our example:
______________________________________________________________________
# This is makefile, used to compile calc.c
# Press the key at appropriate positions!
calc: calc.o parser.o
gcc -o calc calc.o parser.o -lm
# calc depends on two object files: calc.o and parser.o
calc.o: calc.c parser.h
gcc -c calc.c
# calc.o depends on two source files
parser.o: parser.c parser.h xy.h
gcc -c parser.c
# parser.o depends on three source files
# end of makefile.
______________________________________________________________________
Save this file as makefile and type
$ make
to compile your program; alternatively, save it as calc.mak and type
$ make -f calc.mak
And of course, RMP.
You can invoke some help about the C functions, that are covered by
man pages, section 3; for example,
$ man 3 printf
There are lots of libraries available out there; among the first
you'll want to use are ncurses, to handle textmode effects, and
svgalib, to do graphics. If you feel brave enough to tackle X
programming, get XForms ( bloch.phys.uwm.edu/pub/xforms) and/or MGUI (
www.volftp.vol.it/IT/IT/ITALIANI/MORELLO/index.htm), two terrific
libraries that make X programming easy. Moreover, if you can't live
without an IDE a la Borland, get the package xwpe from
sunsite.unc.edu:/pub/Linux/apps/editors/. Chances are you'll like it.
7. The Remaining 1%
7.1. Making Virtual Memory
Although Linux can in theory run with only 2 megs of RAM, the more you
have, the more you can do. X Window System won't run unless you have
at least 8 megs. To create an additional 8 megs of virtual memory,
type as root:
# dd if=/dev/zero of=/swapfile bs=1024 count=8192
# mkswap /swapfile 8192
# sync
# swapon /swapfile
Add the last line in /etc/rc.d/rc.local to make the swapfile available
the next time you boot, or add this line in /etc/fstab:
/swapfile swap swap defaults
7.2. Using tar & gzip
Under Unix there are some widely used applications to archive and
compress files. tar is used to make archives---it's like PKZIP but it
doesn't compress, it only archives. To make a new archive:
$ tar -cvf [file...]
To extract files from an archive:
$ tar -xpvf [file...]
To list the contents of an archive:
$ tar -tf | less
You can compress files using compress, which is obsolete and shouldn't
be used any more, or gzip:
$ compress
$ gzip
that creates a compressed file with extension .Z (compress) or .gz
(gzip). These programs can compress only one file at a time. To
decompress, use:
$ compress -d
$ gzip -d
RMP.
The unarj, zip and unzip (PK??ZIP compatible) utilities are also
available. Files with extension .tar.gz or .tgz (archived with tar,
then compressed with gzip) are as common in the Unix world as .ZIP
files are under DOS. Here's how to list the contents of a .tar.gz
archive:
$ gzip -dc | tar tf - | less
7.3. Installing Applications
First of all: installing packages is root's work. Some Linux
applications are distributed as .tar.gz or .tgz archives, specifically
prepared so that they can be decompressed from / typing the following
command:
# gzip -dc | tar xvf -
The files will be decompressed in the right directory, which will be
created on the fly. Users of the Slackware distribution have a user-
friendly pkgtool program; another is rpm, which is available on all
distributions thanks to Red Hat.
Other packages shouldn't be installed from /; typically, the archive
will contain a directory called pkgname/ and a lot of files and/or
subdirectories under pkgname/. A good rule is to install those
packages from /usr/local. Besides, some packages are distributed as C
or C++ source files, which you'll have to compile to create the
binaries. In most cases, all you have to do is issue make. Obviously,
you'll need the gcc compiler.
7.4. Tips You Can't Do Without
Command completion: pressing when issuing a command will
complete the command line for you. Example: you have to type gcc
this_is_a_long_name.c; typing in gcc thi will suffice. (If you
have other files that start with the same characters, supply enough
characters to resolve any ambiguity.)
Backscrolling: pressing SHIFT + PAG UP (the grey key) allows you to
backscroll a few pages, depending on how much video memory you have.
Resetting the screen: if you happen to more or cat a binary file, your
screen may end up full of garbage. To fix things, blind type reset or
this sequence of characters: echo CTRL-V ESC c RETURN.
Pasting text: in console, see below; in X, click and drag to select
the text in an xterm window, then click the middle button (or the two
buttons together if you have a two-button mouse) to paste. There is
also xclipboard (alas, only for text); don't get confused by its very
slow response.
Using the mouse: install gpm, a mouse driver for the console. Click
and drag to select text, then right click to paste the selected text.
It works across different VCs.
Messages from the kernel: have a look at /var/adm/messages or
/var/log/messages as root to see what the kernel has to tell you,
including bootup messages.
7.5. Useful Programs and Commands
This list reflects my personal preferences and needs, of course.
First of all, where to find them. Since you all know how to surf the
Net and how to use archie and ftp, I'll just give you three of the
most important addresses for Linux: sunsite.unc.edu, tsx-11.mit.edu,
and nic.funet.fi. Please use your nearest mirror.
· at allows you to run programs at a specified date and time;
· awk is a simple yet powerful language to manipulate data files (and
not only). For example, being data.dat your multifield data file,
$ awk '$2 ~ "abc" {print $1, "\t", $4}' data.dat
prints out fields 1 and 4 of every line in data.dat whose second field
contains ``abc''.
· delete-undelete do what their name means;
· df gives you info about the mounted disk(s);
· dosemu allows you to run several (not all) DOS programs---including
Windows 3.x, with a bit of hacking;
· file tells you what filename is (ASCII text, executable,
archive, etc.);
· find (see also Section ``dir'') is one of the most powerful and
useful commands. It's used to find files that match several
characteristics and perform actions on them. General use of find
is:
$ find
where includes search criteria and actions. Examples:
$ find . -type l -exec ls -l {} \;
finds all the files that are symbolic links and shows what they point
to.
$ find / -name "*.old" -ok rm {} \;
finds all the files matching the pattern and deletes them, asking for
your permission first.
$ find . -perm +111
finds all the files whose permissions match 111 (executable).
$ find . -user root
finds all the files that belong to root. Lots of possibilities
here---RMP.
· gnuplot is a brilliant program for scientific plotting;
· grep finds text patterns in files. For example,
$ grep -l "geology" *.tex
lists the files *.tex that contain the word ``geology''. The variant
zgrep works on gzipped files. RMP;
· gzexe compresses executable binaries keeping them executable;
· joe is an excellent editor. Invoking it by typing jstar you'll get
the same key bindings as WordStar and its offspring, including DOS
and Borland's Turbo languages editors;
· less is probably the best text browser, and if properly configured
lets you browse gzipped, tarred, and zipped files as well;
· lpr prints a file in background. To check the status of the
printing queue, use lpq; to remove a file from the printing queue,
use lprm;
· mc is a great file manager;
· pine is a nice e-mailing program;
· script copies to script_file what appears on screen
until you issue the command exit. Useful for debugging;
· sudo allows users to perform some of root's tasks (e.g. formatting
and mounting disks; RMP);
· uname -a gives you info about your system;
· zcat and zless are useful for viewing gzipped text files without
ungzipping them. Possible use:
$ zless textfile.gz
$ zcat textfile.gz | lpr
· The following commands often come in handy: bc, cal, chsh, cmp,
cut, fmt, head, hexdump, nl, passwd, printf, sort, split, strings,
tac, tail, tee, touch, uniq, w, wall, wc, whereis, write, xargs,
znew. RMP.
7.6. Common Extensions and Related Programs
You may come across scores of file extensions. Excluding the more
exotic ones (i.e. fonts, etc.), here's a list of who's what:
·
·
· visualize it; dvips to turn it into a postscript .ps file.
·
·
· info.
·
· containing the description of a package.
· optionally, ghostview.
· gzip.
· Get the package tex, available in many distributions; but beware of
NTeX, which has corrupted fonts and is part of Slackware until
version 96.
·
·
·
·
8. The End, for Now
Congratulations! You have now grasped a little bit of Unix and are
ready to start working. Remember that your knowledge of the system is
still limited, and that you are expected to do more practice with
Linux to use it comfortably. But if all you had to do was get a bunch
of applications and start working with them, I bet that what I
included here is enough.
I'm sure you'll enjoy using Linux and will keep learning more about
it---everybody does. I bet, too, that you'll never go back to DOS! I
hope I made myself understood and did a good service to my 3 or 4
readers.
8.1. Copyright
Unless otherwise stated, Linux HOWTO documents are copyrighted by
their respective authors. Linux HOWTO documents may be reproduced and
distributed in whole or in part, in any medium physical or electronic,
as long as this copyright notice is retained on all copies. Commercial
redistribution is allowed and encouraged; however, the author would
like to be notified of any such distributions.
All translations, derivative works, or aggregate works incorporating
any Linux HOWTO documents must be covered under this copyright notice.
That is, you may not produce a derivative work from a HOWTO and impose
additional restrictions on its distribution. Exceptions to these rules
may be granted under certain conditions; please contact the Linux
HOWTO coordinator at the address given below.
In short, we wish to promote dissemination of this information through
as many channels as possible. However, we do wish to retain copyright
on the HOWTO documents, and would like to be notified of any plans to
redistribute the HOWTOs.
If you have questions, please contact Greg Hankins, the Linux HOWTO
coordinator, at gregh@sunsite.unc.edu via email.
8.2. Disclaimer
``From DOS to Linux HOWTO'' was written by Guido Gonzato,
guido@ibogfs.df.unibo.it. Many thanks to Matt Welsh, the author of
``Linux Installation and Getting Started'', to Ian Jackson, the author
of ``Linux frequently asked questions with answers'', to Giuseppe
Zanetti, the author of ``Linux'', to all the folks who emailed me
suggestions, and especially to Linus Torvalds and GNU who gave us
Linux.
This document is provided ``as is''. I put great effort into writing
it as accurately as I could, but you use the information contained in
it at your own risk. In no event shall I be liable for any damages
resulting from the use of this work.
Feedback is welcome. For any requests, suggestions, flames, etc., feel
free to contact me.
Enjoy Linux and life,
Guido =8-)